Reinforced hoses and other reinforced products, and also reinforcing fabrics, are often exposed to high temperatures during production and/or shaping, and in service. It is also usual for the fabric to be slit, heat-treated and/or to have a textile/matrix adhesive system applied.
A reinforcing fabric may be intimately bonded to a, say, curable rubber or plastics matrix. Under these conditions at least, the fabric should be dimensionally-stable, and should not distort or change its shape when tensioned.
Most woven fabrics used in industrial textile applications have a load-bearing warp and weft and will therefore not distort if tensioned in either direction. However, some textile fabrics are dimensionally less stable once they are released from the control mechanism of their production machines, and will easily distort when tensioned in the longitudinal or transverse direction. Such fabrics are sometimes preferred as reinforcing materials because they facilitate shaping during manufacture of the composite product, e.g. radiator hoses.
An automobile radiator coolant hose and a method for its production are disclosed in U.S. Pat. No. 4,242,296. It is apparently the case that the reinforcing fabric allows the hose material to be deformed to a limited extent only. The hose is produced by using a first extrusion head, for obtaining an inner hose portion onto which the reinforcing fabric is applied, and a second extrusion head for producing an outer hose portion on the fabric. When the second hose portion is applied, the fabric stretches. When the hose material is bent, the reinforcing fabric can be stretched only to a limited extent, so that the bending radius must be large.
EP-A-0100573 describes a method for shaping a hose of material including a reinforcing fabric, and curing the material in the desired shape However, it appears that, when the hose is bent, the fabric will not stretch as much as might be desired and will therefore tear, whereupon the wall of the hose may also tear/burst at the outside of the bend. If the reinforcing fabric does not tear, the inner side of the bend will fold: the internal cross-section of the tube is therefore distorted.
If a conventional reinforcing fabric can be stretched in the longitudinal direction sufficiently to allow bending of the hose, the likely result is that the fabric will stretch during production of a hose, resulting in a change in fabric orientation. The fabric's tensile strength or width may thus be changed undesirably, e.g. by reducing or removing the overlap between the edges of a fabric defining an annulus in a green hose, thus affecting the properties of the product when shaped. In other words, the fabric will not have the desired degree of dimensional stability.
It is an object of the present invention to avoid the disadvantages described above. A particular object behind the present invention is to provide a fabric which can withstand the forces applied to it when incorporated as a reinforcement in a composite product, and be stretched to a limited extent only during this procedure, but which should also allow the product to be bent into a desired shape, while retaining its reinforcing function.